Telegraph system



E. $.SANDBERG Dec.

TELEGRAPH SYSTEM 3 Sheets-Sheet 1 Filed May 25, 1924 Dec. 15 E. s. SANDBERG TELEGRAFH SYSTEM 3 Shoots-Sheet 2 Filed May 23, 1924 gwuentoi;

- [aye/7e d Sandbag Dec. 15,1925. 1.565.507

. E. S. SANDBERG TELEGRAPH SYSTEM Filed May 23. 1924 s Sheets-Sheet s 7! I O r4853 57 49 I I- }29 gwuento'ot ZZ/ye/ve S. Sang/hag telegraph wires.

Patented- Dec. 15, 1925.

. EUGENE SIXTEN SANDBERG, OI INDIANAPOLIS, INDIANA.

TELEGRAPH SYSTEM.

Application filed May 23,

To all whom it concern:

Be it known that I, EUGENE S. SANDBERG,

a citizen of the United States, residing at Indianapolis, in the county of Marion and State of Indiana, have invented certain new and useful Improvements in Telegraph Systems, of which the following is a specification.

This invention pertains to a novel system of electrical communication, having for its object to increase the present capacity of It resides further in the provision of special apparatus particularly adapted for use in the said system.

The invention is capable of embodiment inv various systems of electrical communication, but is especially applicable to what are commonly known to those skilled in the art as bridging duplex circuits. Otherwise stated, this invention consists more specifically in the provision of means for increasing thecapacity of the duplex telegraph.

To this end the invention consists generall y in the provision of means for splitting the main line at each station or terminal into a number of branches or sub-lines, and placing at each end a device for distributing the current from the main line in succession to each of the branches at that end, and arranging means whereby the said devices operate in .synchronism. The preferred embodiment of this invention employs two such branches at each end, and the distributing device employed at each end is preferably a tuning fork or vibrator which is capable of being operated by and kept in synchronism with its mate at the other end by an alternating current transmitted over the main line, the said vibrator being tuned to the frequency of the alternating current. In the accompanying drawings forming part of this specification, in which like numbers of reference denotes like parts wherever they occur,

Figure 1 is schematic diagram of the systern itself;

Figure 2 is a plan View of the special apparatus embodied therein;

Figure 3 is an elevation of the same;

Figure 4: is a sectional view on the irregular line H of Figure 3;

Figure 5 is a fragmentary elevational view of one of the details of the instruments; and

Figure 6 is a sectional view on the line 6-6 of Figure 2.

1924. Serial No. 715,284.

Referring to Figure 1, the main line 1 is divided at one end into branch or sub-lines 2 and 3, and at the otherend into branch or sub-lines 4 and 5. rent from the main line is distributed alternately between the branch lines'2 and 3 at one end by a vibrator 6, and at the other end between the branches 4 and 5 by a similar vibrator 6, to be more completely described hereinafter.

The telegraph cur- As hereinbefore stated, the branch lines 2, 3, 4, and 5 are preferably duplex circuits. Hitherto, in the duplex telegraph, there has been but one such circuit or set at each end of the line connected directly to the line without the intervention of the vibrators 6. There are, of course, different forms of duplex circuits in commercial use at the present time, but the form preferably,

though not. necessarily exclusively, employed herein is known asv the bridging duplex.

The method of operation of the bridging duplex is based on the idea that by placing the polarized relay 7 between the terminals 8 .and 9 of a resistance bridge 10, that the current from the home transmitter will divide at the intermediate bridge terminal 11, half of it going one way to the terminal .8, and the other half of it going the other way to the terminal 9, without any part of the current from the home transmitter entering the relay 7, which is thereby rendered the force of the retractile spring 16 until the battery 17 is brought into the circuit, sending a current through the line in one direction. When the key is opened, the spring 16 pulls the polechanger in the opposite direction to receive current from battery '18, which line in a counter direction to the current fed from the'battery 17. Half of the ourcurrent passes through the.

rent from the pole changer 12 passes 7 negative current causes it to fiip one way,

and a positive current causes it to flip the other way. hen the armature 24 of the relay 7 flips one way, it closes the local circuit 25, including battery 26 and sounder 2", and when it moves the other way, the said circuit is opened. The end of the armature 1 interposed between the poles of the relay 7 is of one polarity, and both poles are of the same strength, but of a polarity opposed to the polarity of the armature. When a current in one direction flows through the relay, one of the core poles becomes weaker, and the other stronger, causing the armature to flip toward the stronger core pole. When the current is reversed, the. opposite condition obtains.- The armature is so adjusted that should there be no current whatever lowing through the relay, it will stick to the side where the last current carried it, WhlCh may be either to the right or the left. It will be obvious that two operators, one at each end, may send simultaneously without interfering with each other.

An inspection of the duplex circuits shown in Figure 1 reveals that, in order to prevent a flow of current through any one of the relays 7 from its home transmitter,

both its artificial line and the main line must be simultaneously either connected or disconnected from the duplex set in which such relay is included. It is, therefore, obvious that, should a current from its home transmitter be flowing through any set, such current, if the main line be momentarily disconnected from the set by the action of the vibrator 6, will be diverted entirely to the unbroken artificial line 19, part of the diverted current going through one leg of the bridge 10, and the other part going through the other leg of the bridge 10 and through the relay. To prevent such accidental operation of the relay, the current from the home transmitter must be interrupted simultaneously with the interruptions in the connection to the main line The distributing vibrator 6 and the two auxiliary vibrators 28 needed at each end of the main line are preferably mounted on a common insulating base or block 29, preferably slate, as shown in Figures 2, 3, 4, and 6. The armatures 30 of the vibrators are constructed of long rods of spring steel, supported at their rear ends in posts 31, secured to the base 29 by bolts 32. The posts 31 are split at their upper. ends to form jaws 33 for clamping the armatures 30, the said jaws being drawn together by screws 34.

The free end of each of the armatures 30 extends between the poles.35 of a pair of electromagnets 36. The poles 35 are preferably bored to fit the cylindrical cores 37 of the electromagnets 36, and are split as at 38 so that they may be tightly secured to the projecting ends of the cores 37 by means of the clamping screws 39. The other ends of the cores 37 project into the yoke 40, which yokes are bored to fit the cores 37 and split as at 41 to permit of clamping around the cores 37 by means of the screws 42. The yoke 40 is secured to the base 1 by screws The ends of the electromagnets 36 adjacent the pole pieces 35 are held within a rectangular frame comprising'side members or posts 44, lower or base member 45, and 11 per member 46, the said members being fastened together in any suitable manner, and the lower member 45 being secured to the base 29 preferably by screws 47.

Cores 37, pole ieces 35, and yoke 40 are fabricated of so iron, and magnetism is induced therein by a permanent magnet 48, of substantially L-shape comprising a major arm 49 extending across the top of the pair of electromagnets 36 from the yoke end to the pole end, and a minor arm 50, depending from the arm 49 at the yoke end. Pintles 51, preferably formed integral with arm 49, project laterally therefrom toward the posts 44, and are pivoted in bearings 52 formed in the ends of screws 53 threading in tapped holes 54 formed in the posts 44. Arm 59 normally tends to gravitate towards yoke 40, but its proximity to the yoke is limited by adjusting screw 55, borne by the projection 56 of brace 46 and impinging against the top of the projection 57 of the free end of the the ma or arm 49.

Contact posts 58 are juxtaposed to the free ends of the armatures 30, being secured to the base 29 by bolts 59. The middle vibrator is the distributor, and it is to be noted that there are two contact posts associated therewith. one on each side of its armature; while the outside vibrators are the auxiliaries and are each provided with but a single contact post. The contact posts are provided with contact screws 69, provided with the usual contact points 61 of platinum-iridium or other suitable conlot tact material, and are prevented from shifting by the usual checknuts 62. The contacts points 61- are contacted by similar contact points 63- on riders or resilient blades 64 secured to the sides of the armature 30. The natural period of vibration of the armatures 30 may be varied by moving the sliders 65 back and sations of the.alternating current passing through the electromagnets 36.

The quantity of magnetism induced in the cores of the electromagnets 36 by the permanent magnet 48 may be varied by adjusting the screw 55 to vary the distance between the yoke 40 and the arm- 50. The greater the percent of magnetism so picked up by the cores, the more intense will the vibration of the armature be for a given value, of alternating current. The pole pieces 35 are, of course, of the same polarity, being alternately strengthened and weakened by the alternating current. Regardless of the amount of current in the coils, the intensity of the vibration can only be determined by the difference of pull between the pole pieces 35 on the armature,-

and this difference is determined by the amount'of permanent magnetism transmitted. to the cores. This magnetism is alternately chopped out by the action of the alternating current. I

Any suitable frequency of alternating current may be used, but the conventional frequency of sixty cycles per second is deemed preferable, the armatures 30 being tuned thereto. Each of the vibrators really constitutes an electric synchronous motor which operates on a surprisingly low current. By winding the coils of the electromagnets 36 to about five-hundred ohms resistance, the armature can actually be kept in synchronism with the alternating current on as low a value as one milliampere of current. The effect of the currents from the telegraph transmitters on the vibrating reeds is practically negligible, for the obvious reason that the vibrating reeds are not in resonance with the irregular pulsations of the telegraph current.

As hereinbefore stated, he middle instrument, on the base 29, the one withthe two contacts, is the distributor that divides the main line into two branches. two instruments operate alternately to one another, each one breaking the current from its associated pole changer 12 when the connection of its duplex circuit to the main line is interrupted by the particular rider on the middle instrument associated with such'duplex circuit. Otherwise, it will be The other manifest that current could flow from the home battery through the home polarized relay when the set was not in contact with the main line, and thus defeat the purpose of the entire scheme.

The three vibrators associated with each terminal 'or. station of the main line have their alternating current electromagnets 68 in series with one another, as depicted in Figure 1, being connected together by wires forming a circuit 68 which is shunted or by-passed-around the duplexing sets from the main line 1 to the ground 69. It should be understood that. alternating current never at any time enters the duplexing sets through the vibrators because the maximum value of the alternating current always occurs when the vibrating reeds 30 are exactly midway in their movements from one side to the other, at which time the riders 64 are not in contact with their respective contact screws 60. It should be understood that when there is no alternating current in.

the main line the vibrator reeds 30 are motionless on center. The circuit 68 includes a high resistance 70, say of approximately twenty-five thousand ohms. and the secondary winding 71 of an alternating current transformer, the primary winding 72 of which receives current through any suitable generator 73. v I

The transformer at one end of the main line is. shown with its primary, switch 74 closed, while the primary switch of the is open, because only one source of alternating current can be used at' one time,

since the two transformers would ordinarily In the arrangement shown in Figure2,

the vibrating reeds 30 of the three instruments on the base 29 are swinging 'in synchronism with one another when the system is in operation. When one reed swings to;the left, all the others swing in the same direction, and vice versa. Furthermore, the reeds 30 at one terminal are in synchronism with the similar reeds at the other terminal. Of course, the instruments on the base 1 may be modified in various ways. For instance, instead of having three reeds at each terminal, there may be only one, which may be so arranged and insulated as to transformer at the other end of the line break the current from both pole changers alternately as well as to distribute the current from the main line. Or, four reeds may be used, the distributor having two, each distributor reed being provided with only one rider.

Prior to the development of the carriercurrent system now in extensive use, it was customary to obtain one and one-half telephone circuits and two telegraph circuits by combining two main line wires, or a pair, as it is termed by those skilled in the art, a complete wholetelephone circuit being obtained from the half telephone circuit by combining two such airs to get what is termed a phantom circuit. This present invention provides two additional telegraph circuits for such a pair The "carrier current system at present in use provides an additional four telephone circuits. By sacrificing the four telephone circuits the -arrier glves, eight telegraph circuits are obtainedin additlon to the original one and one-half telephones and two telegraphs. The present invent-ion can, also, be combined with the carrier sys torn by duplexing its duplexes and still leaving the four carrier telephones and original one and one-half physical telephones available. In other words, it will be possible to get four duplexes and five and one-half telephones as against two duplexes and five and one-half telephones as is at present obtained commercially. Also, by sacrificing the four carrier telephones to obtain eight more telegraph circuits, it is possible to get a total of ten duplexes, which may be further multiplied by the use of the present invention.

Having thus described this invention, I hereby reserve thetbenefit of all changes in form, arrangement, order, or use of parts, as it is evidentthat many'minor changes may be made therein without departing from the spirit ofthis invention or the scope of the following claims.

I claim:

1. An electrical communication system comprising a main line, a plurality of sublines at each end thereof, a distributor at each end operated synchronously by periodically varying current energy transmitted through the main line for connecting the several sub-lines thereat in succession to the .main line, and by-pass circuits at each end the main line for connecting the several sublines thereat in succession to the main line, the said distributor being arranged to make the said connections only when the alternating current is nil, and by-pass circuits at each end for shunting the alternating current around the said sub-lines, the said bypass circuits being adapted to prevent the signalling current from being shorted therethrough.

An electrical communication system comprising a main line, a pair of branch lines at each end thereof, resonant means at each erid operated by periodically modulated current energy from the main line for connecting the branch lines at that end alternately in synehronism with the periodically modulated current, and by-pass circuits 'at each end for shunting the periodically modulated current around the said branch lines, the said by-pass circuits including a source of periodically modulated current energy and a high resistance to prevent the signalling current from being shorted theret-hrough.

4. An electrical communication system comprising a main line; a pair of branch lines at each end thereof, resonant means at each end operated by alternating current from the main line for connecting the branch lines at that end alternately in synchronism with the alternating current, the said means being arranged to make the said connections only when the alternating current is nil; and by-pass circuit-s at each end for shunting the alternating current around the said branch lines, the said bypass circuits each having a high resistance.

5. An electrical communication system comprising a main line, a pair of branch lines at each end thereof, a tuning fork at each end tuned to the frequency of and operated by periodically-pulsating current energy from the main line for alternately connecting the branch lines at that end in synchronism with the periodically-pulsating current, and by-pass circuits at each end for shunting the periodically-pulsating current around the said branch lines.

6. An electrical communication system comprising a main line; a pair of branch lines at each end thereof; a tuning fork at each end tuned to the frequency of and operated by alternating current energy from the main line for alternately connecting, when the alternating current is nil, the branch lines at that end in synchronism with the alternating current; and by-pass circuits at each end for shunting the al.- ternating current around the said branch lines.

7. An electrical communication system comprising a main line, a plurality of duplex circuits at each end thereof, a distributor intermediating each end of the main line and the duplex circuits thereat for connecting such end of the main line to each of its duplex circuits in succession, a by-pass circuit at each end for shunting regularly pulsating current energy from the main line around the duplex circuits, means for interrupting the current from the home transmitter of a duplex circuit when such duplex circuit is disconnected from the main line by its associated distributor, and electromagnetic means included in the bypass circuits and operated synchronously by the regularly pulsating current for driving the said distributors and current interrupting means.

8. An electrical communication system comprising a main line, a pair of duplex circuits at each end thereof, resonant means at each ,end operated synchronously by periodically-varying current energy transmitted through. the main line for alternately connecting the duplex circuits at that end to the main line, resonant means for interrupting the current from the home transmitter of a duplex circuit when such duplex circuit is disconnected from the main line by the said first-mentioned means, the said periodically-yarying current being by passed around the receiving instruments.

9. An electrical communication system comprising a main line, a pair of duplex circuits at each end thereof, vibrating means at each end operated by an electromagnet carrying a periodically-pulsating current for alternately connecting the duplex circuits at that end tothe main line, a vibrator in each duplex circuit operated by an elec- 'tromagnet carrying a periodically-pulsating current for interrupting the current from the home transmitter of such duplex circuit when such circuit is disconnected from the main line by the first-mentioned vibrator, the electromagnets at each end being connected in series with one another in by-pass circuits connected between the main line and the ground at each end.

10. An electrical communication system comprising a main line, a pair of duplex circuits at each end thereof, vibrating means at each end operated by an electromagnet carrying a periodically-pulsating current for alternately connecting the du lex circuits at that end to the main line, a vibrator in each duplex circuit operated by an electromagnet carrying a periodicallypulsating current for interrupting the current from the home transmitter of such duplex circuits when such circuit is disconnected from the main line by the first-mentioned vibrator, the electromagnets at each end being connected in series with one another in by-pass circuits connected between the main line and the ground at each en'd, the said by-pass circuits each containing a high resistance.

11. An electrical communication system comprising a main line, a pair of duplex circuits at each end thereof, vibrating means at each end operated by an electromagnet carrying a periodicall -pulsating current for aiternatel-y connecting the duplex circuits at that end to the main line, a vibrator in each duplex circuit operated by an electromagnet carrying a periodically-pulsating current for interrupting the current from the home transmitter of such duplex circuit when such circuit is disconnected from the main line by the first-mentioned vibrator, the electromagn'ets at each end being connected in series with one another in by-pass circuits connected between the main line and the ground at each end, the said by-pass circuits each containing a source of periodically-pulsating current. 12. An electrical communication system comprising a main line, a pair of duplex circuits at each end thereof, vibrating means at each end operated by an electromagnet carrying a periodically-pulsating current for alternately connecting the duplex circuits at that end to the main line, a vibrator in each duplex circuit operated by an electromagnet carrying a periodically-pulsating 1 current for interrupting the current from the home transmitter of such duplex circuit when such circuit is disconnected from the main line by the first-mentioned vibrator, the electromagnets at each end being connected in series with one another in by-pass circuits connected between the .main line and the ground at each end, the said by-pass a high resistance,

circuits each containin and a sourse of periodically-pulsating current.

In testimony whereof I hereunto aflix my signature. I

EUGENE SIXTEN SANDBERG. 

